Question

Force $F$ is applied on upper pulley. If $F=30t$ where $t$ is the time in second. Find the time when $m_1$ loses contact with the floor.

• A. $2sec$
• B. $4sec$
• C. $6sec$
• D. $8sec$

Answer 1

The correct option is A $2sec$

Here, $2T=m_{1}g=4\left(10\right)=40\Rightarrow T=20N$
and $F=T+T+T=30t$
$t=\frac{3T}{30}=\frac{3\left(20\right)}{30}=2sec$